Wave signaling system



April 18, 1939. H, M. LEWIS- WAVE SIGNALING SYSTEM 2 Sheets-Shes t 2 Filed May 6, 1951 QQS S QB e/e5 per 3 for Sea le E INVENTOR Harold f7, Jew/ls Y @M M CZ ATTORNEYS Patented Apr. 18, 1939 UNITED STAKES EPATENT OFFiCE WAVE SIGNALING SYSTEM Harold M. Lewis, Dougleston, Long Island, N. Y.,

assignor to Hazeltine Corporation, a. corporation of Delaware Application May 6, 1931, Serial No. 535,328

16 Claims. (Cl. 178--5.6)

This invention relates to the simultaneous the ratio of the tuned frequencies of the plutransmission and reception of a plurality of sigrality of receiving circuits remains constant over mils and more particularly to a system for the the range of operation and is equal to the ratio transmission and reception of signals wherein a of the plurality of carrier frequencies of the receiving station can be adjusted to receive the transmitting stations. 5 plurality of signals transmitted from any of a In some embodiments of the invention, a sepanumber of transmitting stations. rate antenna is employed for each channel of the A prime purpose of the invention is to provide receiving station; in other embodiments a coma system wherein the plurality of signals simulmon antenna is employed and the proper signals taneously transmitted by a transmitting station from the antenna are impressed upon the indi- 10 comprises a signal corresponding to acoustic vidual receiving circuits by means of appropriate Waves and a signal corresponding to visual, or input circuits. television, waves. In another embodiment of the invention, the In accordance with this invention, it is contemreceiving station is adapted to receive signals of plated to so organize each transmitting and rea type in which only a single sideband and no 15 ceiving station of the general system that any of carrier, for each signal, is transmitted. In this the receiving stations can readily be adjusted to embodiment, the missing carriers are supplied by receive the simultaneous visual and acoustic prolocal oscillators. A. feature of this arrangement gram of any of the transmitting stations. In is a means for tuning the receiving channel at 0 other words, by utilizing the principles of this inthe middle of the sideband when the associated vention, there can be developed a broadcast syslocal oscillator is tuned at the frequency of the tern of combined acoustic and visual programs, missing carrier. in a manner analogous to the present system for Another embodiment comprises a receiving stabroadcasting and receiving acoustic programs. tion including superheterodyne receivers. This The invention is effected by assigning to each arrangement may be adapted for the single sideof the transmitting stations of the general sysband transmission or for the usual type of transtem definite frequencies for the carrier waves of mission in which the carrier and both sidebands the plurality of programs transmitted; there is, are transmitted. furthermore, assigned to the associated carrier The invention will be better understood from waves of each station a certain ratio of frethe following detailed description when read in 30 quencies which is the same for all the transmitconjunction with the drawings, of which: ting stations. The preferred manner of assign- Fig. 1 illustrates schematically a dual signal ing to the associated carrier waves of each statransmitting station in accordance with this intion the required definite ratio, is to utilize cervention; tain definite harmonics of a frequency determi- Figs. 2 and 3 illustrate graphically on polar 00- 35 nating element. Each of the carrier waves of a ordinates the method of frequency allocation emstation is transmitted from an individual transployed in accordance with this invention in transmitting circuit. mitting and receiving a plurality of signals simul- The receiving stations of the general system of taneously; I this invention comprise a plurality of receiving Fig. 4 illustrates schematically a receiving stacircuits corresponding to the transmitting cirtion, in accordance with this invention, adapted cuits of the transmitting stations. Each of the to receive the dual transmission signals from a receiving circuits of a receiving station is adapted transmitting station like that of Fig. 1;

to select and detect the modulated carrier signal Fig. 5 shows schematically a superheterodyne 5 radiated from the corresponding transmitting type of receiving station embodying the invencircuit of a transmitting station. 1 tion. 7 To enable any receiving station to be tuned to Since the invention is directed primarily to a the tr ns ed Signals of any transmitting t system for the combined transmission of signals tion, each receiving channel, or circuit of the recorresponding to vision and to sound, it will be ceiving station, is provided with one or more the practice throughout this specification to refer 50 tunable circuits. The tunable circuits of each reto those frequencies having their origin in light ceiving channel are caused to vary in accordance as vision signals, or vision frequencies, and to with the same law of tuning control versus frethose frequencies having their origin in sound, as quency variation between the same ratio of maxisound or acoustic signals or frequencies. It is mum to minimum frequency; and furthermore, necessary to make this distinction owing to the 55 ill fact that the signals having their origin in sound occupy in part the same frequency range as signals having their origin in light, prior to modulation with the carrier frequency. For example, the sound frequency range is approximately 50-6,000 cycles per second, and the vision frequency range is approximately 16-50,000 cycles per second.

Fig. 1. illustrates schematically a transmitting station in accordancewith this invention which is adapted to transmit simultaneously acoustic and vision signals. The individual elements of the station are illustrated in generalized form; since they are not novel in themselves, there is no point in illustrating or describing them in detail. The station comprises two branches, or channels, designated generally as I and II, the upper branch of which is a circuit adapted to transmit vision frequency modulated signals and the lower branch of which is a circuit adapted to transmit acoustic frequency modulated signals. In this and following figures the subscript v designates apparatus associated with the vision circuit, and subscript a designates apparatus associated with the acoustic circuit.

The system comprises a frequency determining element 9, label F, which is connected with both the acoustic and vision circuits and is adapted to impress upon both these circuits oscillations of a definite fixed frequency. The frequency determining element may be any well-known arrangement for providing a constant frequency, such as a piezo electric crystal controlled oscillator.

The vision branch, or circuit, III of the station comprises a harmonic generator l2, for genera-ting a certain harmonic of the frequency determining element 9, which is the carrier wave of the vision circuit. The vision carrier signal is amplified by an amplifier l3. The amplified carrier signals are impressed upon a modulator 14, upon which is also impressed signals from a second amplifier l5, which amplifies signals generated in a photo-electric cell [6 by means of a television scanning disc IT. The modulated output of modulator I4 is amplified by an amplifier l8. From the output of the latter amplifier the band of frequencies corresponding to a vision frequency modulated wave is radiated from an antenna IS.

The acoustic circuit II is arranged in a fashion analogous to the arrangement of the vision channel I 0, the subscript a designating the elements of this circuit. The corresponding elements of the acoustic and of the vision circuits are designated by the same numerals except that in the case of the acoustic circuit the numerals are primed. In place of the scanning disc and photo-electric cell of the vision circuit, the acoustic circuit is provided with the usual microphone 20.

The operation of the individual vision and acoustic circuits l0 and II and the component elements of these circuits are well known in the art and require no extended discussion here.

One manner of allocating the respective vision and acoustic carrier frequencies in a general broadcasting system comprising many transmitting stations of the type illustrated in Fig. l, is shown graphically in Fig. 2. Fig. 2 is a polar chart having three angular scales A, B and C. The inner scale A represents fundamental frequencies, that is, the frequencies of the frequency determining elements F of all the stations of the general broadcast system. For convenience, and

in order to provide a uniform frequency separation between the transmitting carrier signals of all the stations of the system, the separation between the generated frequencies of the elements F of the individual transmitting stations is made 2 kilocycles per second. Thus, if the frequency generated by the element F of a certain station be 100 kilocycles per second, the frequency of the corresponding element of F of a second station which radiates signals closest in the frequency spectrum to those of the first station, will be 102 kilocycles per second.

Scale B represents the acoustic carrier signal frequencies radiated from the acoustic circuits of the stations.

In the case of the particular arrangement of the broadcast stations now being described, the acoustic carrier frequency for all the stations is selected as the fifth harmonic of the fundamental frequency of the element F. This fifth harmonic is obtained by adjusting the selective amplifier circuit l3 associated with harmonic generator l2 to select the fifth harmonic of the element F.

Since the fifth harmonic has been selected asthe acoustic carrier frequency, it follows that the separation between the acoustic carrier frequencies of the several stations of the system will be kilocycles per second as in the case of the present day acoustic broadcasting. This 10-kilocycle station separation is illustrated by the crosshatched section at 850 kilocycles on scale B, the width of this cross-hatched section being 10 kilocycles. The corresponding vision frequency sepa ration is indicated by the width of the crosshatched section at 3,060 kilocycles on scale C.

Scale C represents the vision carrier frequencies of the stations. In the present system the vision carrier frequencies are selected as the eighteenth harmonic of the frequency determining elements F. It likewise follows that the separation between adjacent vision carrier frequencies in this case is 36 kilccycles per second, which is ade-, quate for transmitting a television image of moderate detail.

In this case the ratio K between the two carrier frequencies is a constant and is expressed by:

six 18 a x5 6 Any other harmonic frequencies might be sei lected, it being only necessary that the relation between the two carrier frequencies shall be the ratio of two integers and hence a constant for all stations operated in accordance with the proposed system. It is, of course, desirable that the acoustic carrier frequencies of all stations of the general system should cover the present day broadcasting range of 500 to 1500 kilocycles per second, as illustrated by scale B of Fig. 2. It is further desirable that the vision carrier frequencies shall be high so that the frequency separation between adjacent ohannels is large, in order that an image of good detail may be reproduced.

Referring for the moment to Fig. 1, it should be noted that the harmonics of both the vision and of the acoustic circuits could be selected from a single harmonic generator instead of two separate harmonic generators, as illustrated. In

case a single harmonic generator is employed,

required that the quality of there would be required in each of the transmitting circuits, a selective circuit for selecting the proper harmonic to be employed as the carrier frequency.

Furthermore, if the fundamental frequency of the frequency determining element F be chosen to be the correct frequency for the acoustic carrier wave, then the harmonic generator in the acoustic circuit may be omitted and the situation is that illustrated graphically in Fig. 3.

Fig. 3 is a polar chart similar to Fig. 2. Scale D of Fig. 3 represents the range of fundamental frequencies of the frequency determining elements of all the transmitting stations, which in this case are the acoustic carrier frequencies. Scale E represents the range of vision carrier frequencies in a case in which the third harmonic of the fundamental frequency is employed. In this case K equals 3, and the frequency separation for the television carrier frequencies is 30 kilocycles per second since the frequency separation of the acoustic carrier frequencies is taken as 10 kilocycles per second. The outer scale G represents the range of vision carrier frequencies when the tenth harmonic is selected; in this event the frequency separation of the vision carrier waves is kilocycles per second. The widths of the cross-hatched sections indicate the frequency separations for the three scales, where the carrier frequency separation of scale D is made 10 kilocycles per second.

As a specific example, suppose a transmitting station to have the acoustic carrier frequency set at 860 kilocycles per second; then, if it be not the television transmission be exceptionally good, the third harmonic may be selected for this purpose; that is, the vision carrier frequency will be 2580 kilocycles per second. On the other hand, for transmitting an image of much finer detail, the tenth harmonic may be selected, thereby allowing a band width of 100 kilocycles per second, which will require a carrier frequency of 8600 kilocycles per second.

Regardless of which harmonic is selected as the vision carrier frequency, it is essential in order to provide a general broadcast system in accordance with this invention, in which the program from any transmitting station may be selected by a receiving station by means of a single tuning arrangement, that the same harmonic be selected for the vision carrier frequency of each transmitting station.

The statement that the ratio between the transmitted carriers from any one station shall be the ratio of two integers, applies only to the arrangement in Fig. 1 where a common frequency determining element F is used. This arrangement has the distinct advantage that any variation of produces corresponding changes in v and fa without changing their ratio K. However, the invention may be practiced with individual, independent frequency determining elements for the vision and acoustic branches and the ratio of carrier frequencies may be any number and need not necessarily be a harmonic ratio, provided that all stations in the system likewise have the same ratio between the carrier frequencies which they transmit.

Fig. 4 illustrates a receiving station adapted to receive programs broadcast from any of a number of stations like that of Fig. 1. The station comprises two main branches, or circuits, corresponding to the two transmission circuits of Fig. l. The upper circuit 35 is the vision receiving circuit and the lower circuit 35' is the acoustic re ceiving circuit. Both circuits constitute in themselves individual receiving circuits such as are commonly employed in radio reception.

Referring to the acoustic branch 35, the circuit comprises a receiving antenna 2| connected to the input of a radio-frequency amplifier 22. The radio-frequency amplifier is shown in symbolic form as comprising amplifier tubes 23 and 24, and selective circuits 25, 26 and 21'. The output of the radio-frequency amplifier is connected to the input of a detector 28, the output of which is connected through the usual audiofrequency amplifier 29 to a loud speaker 30'.

A local oscillator 3i is shown in dotted lines associated with the detector 28. For the present system in which signals are transmitted by means of modulated carrier signals, the local oscillator is not required; the necessity for the oscillator only rises in the case of a transmission system in which only the side bands, without the carrier, are transmitted; such a system will be described subsequently.

The vision circuit of the receiving station is analogous to the acoustic system, and the corresponding elements are similarly numbered except that in the case of the vision system, the numbers are not primed. Moreover, since the frequency range of the vision signals is different from that of the acoustic signals, the amplifiers 22 and 29 are adapted to transmit a different range than the corresponding amplifiers 22 and 29' of the acoustic circuit. Moreover, in the vision system a light valve 30 and the usual associated scanning disc 32 are used in place of the loud speaker 30'.

The selective circuits of the vision and acoustic receiving circuits are provided with a uni-control arrangement 33 which is operatively connected to the selective circuits of the two receiving circuits for allowing simultaneous tuning of the two circuits.

It will be assumed for the moment that the transmission from both the acoustic and vision branches of the transmitting station of Fig. l is by means of the usual modulated carrier waves, that is, a carrier and both side bands. Furthermore, it is assumed that both the acoustic and the vision carrier frequencies transmitted to the station have the harmonic relation previously described. Then, in order for the receiving station of Fig. 2 to receive simultaneously the vision and acoustic program, the same harmonic relation must exist between the resonant frequencies to which the two branches of the receiver are tuned. Since, in accordance with the general broadcast system contemplated herein, there are other transmitting stations transmitting a dual program of vision and sound in a manner similar to that of Fig. 1, and also employing the same harmonic relationship or ratio between acoustic and vision carrier frequencies, it is essential, in order that the receiver may be tuned to select the program of any one of these stations by means of the single control device 33, that certain conditions as to the circuit elements, both fixed and variable, be determined and maintained.

In the first place, all the transmitters should be assigned carrier frequencies within a certain broadcast band of frequencies, in the manner illustrated in the charts of Figs. 2 and 3. The receiving station must then be equipped with variable tuning circuits adapted to tune over this entire broadcast frequency band. If, for exampie, the tuning system for the acoustic receiving branch'is arranged to tune between the frequency limits of 500 to 1500 kilocycles per second, as in present day broadcasting, that is, a three-to-one frequency range, then the tuning circuits for the vision receiving branch must be adapted to tune over the same three-to-one range of frequency variation, and its total range will be determined by the particular ratio of carrier frequencies selected. For example, where a ratio of ten is employed, the range of vision carrier frequencies will extend from 5000 to 15,000 kilocycles per second.

Another requirement is that the law of frequency variation with movement of the control device 33 must be the same for both the acoustic and the vision receiving systems. For example, the law of variation may be of any of the wellknown types such as, straight-line frequency, straight-line capacity, and logarithmic, or hyperbolic.

It will therefore be clear that in fulfilling the two requirements, (1) by making the variable tuning elements of both branches similar in their law of frequency variation with control, and (2) by making the relation of maximum to minimum frequency over which they tune the same for both branches, it then follows that the proper relative choice of the fixed constants of the tuned circuits of the two branches will determine the ratio K of the two branches to be the same as that of the two carrier frequencies being received from any of the transmitters of the system. Furthermore, the ratio K will be maintained constant for any position of the control knob 33 as it is rotated to simultaneously vary the tuning of branches 35 and 35'.

In the operation, then, it is simply necessary to tune the receiver until the maximum acoustic reception is obtained and automatically the vision image will be simultaneously tuned in.

The easiest method of fulfilling the single control requirements of the situation described above is to employ in the selective circuits interleaving plate condensers having similar plates so that their laws of variation are the same, and to adjust the minimum circuit capacities so that all condensers operate in accordance with the same law of variation between the maximum and minimum capacity limits required by the particular range of tuned frequencies employed. For example, regardless of absolute values of capacity, in order to realize a maximum frequency variation of 3 to 1, all the tuning condensers would be required to provide a capacity variation of 9 to 1; this assumes that the associated inductances are fixed. The tuning condensers of the vision radio-frequency amplifier 22 would preferably be all alike, as would also the tuning condensers of the acoustic radio-frequency amplifier 22'.

It should be understood, of course, that the tuning could be accomplished by means of variable inductances instead of variable capacities, or else, both variable inductances and variable capacities might be utilized. It would further be possible to obtain identical laws of frequency variation by utilizing dissimilar tuning elements and then correcting for the dissimilarity by means of a cam or other non-linear mechanical link between the mechanical tuning control 33 and the variable tuning elements.

In addition to the transmission system just described in which the signals are transmitted by means of a carrier wave and two associated side bands, there is also known an improved form of transmission, known as single sideband transmission, which has among other advantages the advantage that no carrier frequency is radiated from the transmitter; the only radiation is that of a single side band.

This form of transmission could be obtained in the transmitting station of Fig. 1 by the inclusion of appropriate filters and balanced circuits for suppressing the carriers and the unwanted side bands.

By virtue of the fact that there is present no relatively strong carrier signal, there are eliminated to a large extent disturbances due to interference of the carrier signal with other waves. A further advantage is that the side-band width may be doubled where there are utilized frequency transmission channels of the same width, thereby providing greater intelligence definition. In such a communication system it is necessary to supply the carrier signal locally at the receiver so that the modulation of the incoming side band with the local carrier wave will yield the original signal frequencies.

The receiving station of Fig. 4 may be readily adapted to receive signals transmitted by the single side band system. This may be accomplished by adding the local oscillators 3! and 3|, respectively, illustrated symbolically by dotted lines, to the vision and acoustic circuits. Each of these local oscillators has a tuning circuit 34 and 34', respectively, for adjusting the oscillator to the proper carrier frequency. These oscillator tuning circuits are connected with the unicontrol 33 in such a manner that each oscillator is tuned to the same frequency to which the radio-frequency amplifier of the associated branch is tuned. The band of frequencies transmitted by the radio-frequency amplifier at each tuning point is broad enough so that the entire side band is transmitted throughout. The side band combines with the locally generated frequency in the detector in the well-known manner to yield in the output of the detector the original vision or acoustic signals.

In the above instance, the full advantage of the width of the resonance band of the vision radiofrequency amplifier 22 is not realized since the resonant frequency is at the edge rather than at the middle of the side band of frequencies being received. It is desirable, especially for television purposes, to tune the radio-frequency amplifier at the middle of the side band in order that a broad range of side band frequencies may be transmitted. This latter desired condition may be obtained by keeping the ratio K constant as before, between the tuning of 3| and 3|, but at the same time maintaining a predetermined frequency difference between the oscillator frequency and the tuning frequency of the radiofrequency amplifier. This frequency difference should be about half the sideband width, the frequency of the amplifier being either uniformly higher or lower than the frequency of its local oscillator according to whether the single side band transmitted is the upper or the lower s de band.

For example, assume that the upper side band be transmitted by all the television branches of each transmitter, the lower side band and the carrier being suppressed, and that the television side band width is kilocycles per second. Then the tuning of the radio-frequency amplifier should be arranged with respect to the tuning circuit of the local oscillator so that the freequency generated by the oscillator is 50 kilocycles per second below the frequency to which the radio-frequency amplifier is tuned. The frequency difference between the oscillator and the radio-frequency amplifier must be maintained constant throughout the tuning range of operation.

Such maintenance of a predetermined frequency difference between the tuning circuits of the radio-frequency amplifier and of the local oscillator may be readily realized by'using for the variable tuning elements apparatus characterized by straight-line frequency type of tuning. For example, the use of variable condensers with plates so shaped that the law of frequency variation with angular movement of the plates is linear, provides this relation; hence, the fixed frequency difference may be provided for by setting the plates of the tuning condenser of the oscillator at such an angle relative to the plates of the radio-frequency amplifier tuning condensers that there exists between the respective resonant frequencies the desired frequency difference.

Another method of obtaining the desired frequency difference between the oscillator and radio-frequency amplifier is to employ a fixed capacity in conjunction with the variable condenser. All the variable condensers would in this case be identical for both the radio-frequency amplifler and for the local oscillator.

When single side-band transmission is employed for both the vision and the acoustic broadcast, it is preferable to arrange all the transmitters so that all television and acoustic branches will always transmit the upper side band only, or conversely all will transmit the lower side band only.

Regardless of whether or not any or all of the carrier frequencies of a transmitting station are suppressed prior to radiation from the antenna, it is essential in the specific embodiments described that the carrier frequencies shall bear to each other the same constant ratio K.

Fig. 5 illustrates a dual program receiving station of which the individual receivers are of the superheterodyne type. The station comprises two circuits, or branches, 50 and 59 for television and acoustic reception, respectively. The acoustic reception circuit comprises a radio-frequency amplifier 5| which is similar to radiofrequency amplifier 22' of Fig. 4. The output of amplifier 5| is transmitted to a first detector 52' with which is also associated a local oscillator 53'. As a result of the combination in the first detector of the local oscillator frequency and the signal frequency at the output of the radiofrequency amplifier, there is produced at the output of the first detector the wellknown modulation products which includes the frequencies which represent the difference between the signal frequencies and the local oscillator frequencies. These difference frequencies which are produced in superheterodyne types of receivers are commonly called intermediate frequencies. The intermediate frequencies are properly selected and amplified by an intermediate frequency amplifier 54, the output of which is impressed upon a second detector 55'. The second detector operates in the well-known manner to produce at its output the audio-frequency component, which is amplified by an audio-frequency amplifier 56, and applied to a loud speaker 51'.

The television receiving circuit 50 is arranged in the same manner as the acoustic receiving circuit 50, except that the usual light valve 58 and scanner 59 are incorporated in place of the loud speaker 57 of the acoustic circuit.

In the arrangement of Fig. 5 there is employed a single antenna which intercepts and supplies, simultaneously, vision signals to the vision receiving branch, and acoustic signals to the acoustic receiving branch. The two branches are effectively connected in parallel with the circuit comprising the antenna til and ground ti. One of these parallel antenna circuit connections, namely, the one which includes the input to the vision circuit, includes a band pass filter 62 which freely transmits the entire range of the vision signals transmitted by all the transmitting stations of the general broadcast system, but greatly attenuates all other frequencies including the acoustic broadcast range. Likewise, the antenna circuit connection which includes the input of the acoustic receiver includes series therewith a band-pass filter E53 which freely transmits the entire acoustic broadcast range, but greatly attenuates all other frequencies including the vision broadcast range. In this manner the acoustic and vision signals are effectively confined to their respective receiving circuits. The receiver is provided with a uni-control arrangement 54 which operates upon the selective circuits of radio-frequency amplifiers 5| and 5i and of oscillators 53 and 53 in the manner described in connection with Fig. 4.

For uni-control operation, the necessary conditions to be maintained are that as indicated previously, and also that thefollowing relations be maintained:

for; represents the frequency generated by oscillator 53';

it. represents the frequency to which interme diate frequency amplifier 54 is tuned; and

fa represents the frequency to which intermediate frequency amplifier 54' is tuned.

The above equations represent the condition in which the local oscillators are tuned to frequencies lower than those of the associated carrier waves.

The receiving apparatus may be enclosed in a cabinet represented by the enclosures 56. Other well-known refinements may be incorporated, such as a rectified filtered source of alternating current for supplying the electrode potentials to the vacuum tubes.

In the event that the single side band type of transmission is employed, the missing carrier frequency may be furnished in the manner described in connection with Fig. 4, that is, an additional local oscillator may be associated with each of the first detectors 52 and 52. A simple procedure, however, is to provide only a single oscillator for this purpose, such as the oscillator 65 indicated in broken lines; the output of this oscillator is connected to both detectors 55 and 55'. This arrangement, which utilizes only a single local oscillator for supplying the missing the second detector, it is still desirable that the radio-frequency amplifiers shall tune at the middle of the side band. This may be accomplished by the method described in connection with the receiver of Fig. 4. For the case where only the upper side bands are being transmitted the relation to be maintained then is:

fs,,=fv+f fs =fa+f and fV fS f f; fs,,f where ft is the suppressed carrier of the vision transmitter fa is the suppressed carrier of the acoustic transmitter fsv is the middle frequency of the vision side band film is the middle frequency of the acoustic side band fl is the middle frequency of the vision signaling frequencies I2 is the middle frequency of the acoustic signaling frequencies Although the invention has been specifically described in respect to the dual transmission and reception of television and acoustic programs, it should be understood that the invention extends as well to the transmission of other types of programs. In other words, this system of broadcast transmission and reception is applicable whenever it is desired for any reason to separately transmit the several component parts of a unified performance. Furthermore, it is possible to transmit and receive more than two programs simultaneously by increasing accordingly the number of branches of the transmitters and receivers. For example, more channels would be required if voice and television in color are to be broadcast. One channel would then be required for the acoustic signals, another for the vision signals of one component color and a third for the vision signals of another component color. In the latter event the arrangement of the transmitting frequency ranges would be similar to that of Fig. 3 wherein the carrier frequencies of the three transmitting programs are in accordance with the three scales of the figure.

It should be further understood that although radio transmission has been specifically described, the invention is equally applicable to any system of carrier transmission, including Wire transmission.

What is claimed is:

1. A broadcasting system comprising a plurality of transmitting stations, each of said stations including means for transmitting a plurality of interrelated signals each of which is a part of a unified performance, said plurality of signals transmitted by each station bearing the same harmonic relation to each other, and a receiving station equipped with tunable means for simultaneously and separately selecting from a plurality of bands in frequency, signals from each band having said harmonic relation to each other, whereby each of said plurality of signals transmitted by any one of said transmitting stations may be simultaneously and separately utilized at said receiving station to reproduce said unified performance.

2. A system of broadcasting, comprising at least two transmitting stations and at least one receiving station, each of said transmitting stations including means for simultaneously transmitting a plurality of signals each of which is part of a unified performance, the constant carrier'frequencies of each of which bear the same fixed percentage relation to each other and said receiving station comprising means for simultaneously selecting and individually and simultaneously reproducing intelligence correspond ing to the signals from any one of said transmitting stations to reproduce said unified performance, said selecting means comprising a unicontrol arrangement which simultaneously adjusts a separate tuning circuit in resonance with each of said signals from one of said transmitting stations.

3. A system of broadcasting which comprises a plurality of transmitting stations and atleast one receiving station, each of said transmitting stations including means for simultaneously transmitting the component parts of a unified performance as a plurality of signals each of which has a carrier wave, each of the carrier Waves of each station bearing a fixed ratio relation to each other which is the same for all the transmitting stations of said broadcasting sys tem, and said receiving station comprising means for individually selecting said signals and means for individually and simultaneously reproducing intelligence corresponding to each of said plurality of signals to reproduce said unified performance, said selecting means comprising a uni-control arrangement which is adapted to cause the resonant frequencies of said individual selecting means to bear the same ratio relation to each other, over a large rangeof uni-control operation, as said carrier waves bear to each other, whereby said receiving station may be tuned to select the signals from any'of the transmitting stations. ,7

4. A radioreceiving system for simultaneously receiving signals corresponding to sound and signals corresponding to vision, which signals occupy frequency bands which bear a definite harmonic relation to each other, comprising a receiving circuit for said vision signals and a receiving circuit for said acoustic signals, each of said circuits including a radio-frequency amplifier having associated therewith adjustable tuning circuits, and uni-control means connected with said tuning circuits in such a manner that throughout the range of operation of said uni-control the tuned frequencies of said acoustic circuit and of said vision circuits bear the said harmonic relation to each other.

5. A radio receiving system for simultaneously receiving signals corresponding to vision and signals corresponding to acoustic waves, comprising a receiving circuit for said vision signals and a receiving circuit for said acoustic signals, each of said receiving circuits including a variable frequency-selecting circuit, a local oscillator having a variable circuit for tuning its output frequency and a detector associated with said selecting circuit and with said local oscillator, whereby said signals modulate with the waves from said local oscillator in said detector, and uni-control means connected to the variable selective circuit and to the variable tuning circuit of the oscillator of each receiving circuit in such relation that there is a fixed. ratio between the tuned frequencies of the selective circuits of said receiving circuits, and a constant difference maintained between each local oscillator fre quency and the associated selective circuit frequency.

6. A radio receiving system for the simultaneous reception of broadcast signals corresponding to sound and to vision, said broadcast signals being of the type in which the carrier wave is suppressed and only a single side band corresponding to each signal is transmitted, said system comprising a receiving circuit for the signals corresponding to vision and a receiving circuit for the signals corresponding to sound, each of said circuits including a signal selecting circuit, a variable-frequency local oscillator having a variable tuning circuit and a modulator associated with said signal selecting circuit and with said local oscillator, and uni-control means operatively connected with the signal selecting circuits and local oscillator tuning circuits of both of said receiving circuits, in such relation that when the vision receiving circuit oscillator is tuned to the frequency of the suppressed vision carrier wave, the sound receiving circuit oscillator is tuned to the frequency of the suppressed sound carrier wave and said signal selecting circuits are tuned respectively to the vision and sound frequency sidebands.

'7. A system for the simultaneous reception of a plurality of signals, each of said signals bearing a fixed relation to each other, said system comprising a plurality of receiving circuits of the superheterodyne type, corresponding to the number of signals to be simultaneously received, each of said superheterodyne circuits including a signal frequency variable tuning circuit, a first modulator coupled to said tuning circuit, a local oscillator having a frequency-determining circuit, coupled to said modulator, a tuned intermediate frequency amplifier for amplifying the modulation product of said oscillator frequency and said signal frequency, a second detector connected to the output of said intermediate frequency amplifier and uni-control means operatively connected with said tuning circuit and with said frequency determining circuit of each superheterodyne circuit in a manner to maintain said fixed relation between the tuning frequencies of said tuning circuits and to simultaneously adjust the frequency-determining circuits of said local oscillators so that the modulation products are within the frequency ranges of said tuned intermediate frequency amplifiers.

8. A system in accordance with claim 7 in which said received signals are of the type in which only a single side band corresponding to each signal, and no carrier, is received, and a second local oscillator associated with each of -said second detectors, the frequency of each of adjusted so that the intermediate frequencies of all said superheterodyne receiving circuits are the same, and a single second local oscillator, connected with all of the said second detectors,

the frequency of said second oscillator being equal to the intermediate frequency.

10. A radio receiving station adapted to receive simultaneously at least two signals, said station comprising an individual receiving circuit for each of said signals, tuning means associated with each of said circuits and a uni-control device for simultaneously operating the tuning means of said circuits from a maximum to a minimum tuning frequency which is different for each of said circuits, the ratio of maximum to minimum, and also the law of frequency variation with uni-control movement being the same for each of said tuning means.

11. A radio receiving station comprising a plurality of receiving circuits adapted to simultaneously receive and reproduce intelligence, each of said circuits including means for tuning over a; band in frequency, and uni-control means connected with said tuning means, the fixed and variable circuit constants of both circuits being chosen so that the ratio of the frequencies to which the two circuits are resonant is constant as the uni-control means is varied to tune each circuit over its respective band in frequency.

12. A system of broadcasting comprising at least two transmitting stations and at least one receiving station, each of said transmitting stations including means for simultaneously transmitting a plurality of signals, and. each receiving station being adapted to receive each of the signals transmitted by one of said transmitting stations, said receiving stations each comprising individual receiving circuits for each of said signals, tuning means associated with each of said circuits and a uni-control means for simultaneously operating the tuning means of said circuits, the ratio of the adjacent frequencies of the various signals transmitted by each transmitting station being the same, and the fixed and variable constants of each receiving circuit being chosen so that the ratio of the frequency of each signal to that of the adjacent signal being received is the same, and the same as that of the signals transmitted by each of said transmitters.

13. A radio receiving system for simultaneously receiving signals in a plurality of signal channels, said signal channels occupying frequency bands which bear a definite harmonic relation to each other, comprising a receiving circuit for each of said channels, each of said circuits including a tunable frequency selecting system, and uni-control means connected with said frequency selecting circuits in such a manner that throughout the range of operation of said uni-control the tuned frequencies of said plurality of signal channels bear the said harmonic relation to each other.

14. A radio receiving system for simultaneously receiving signals corresponding to sound and signals corresponding to vision, which signals occupy frequency bands which bear a definite harmonic relation to each other, comprising a receiving circuit for said vision signals and a receiving circuit for said acoustic signals, each of said circuits including a frequency selecting circuit having associated therewith an adjustable tuning element, and uni-control means connected with said tuning elements in such a manner that throughout the range of operation of said unicontrol means the tuned frequencies of said acoustic circuit and of said vision circuit bear the said harmonic relation to each other.

15. In a television system; a plurality of broadcasting stations for transmitting television and sound signals; means whereby each of said stations transmits carrier currents modulated by said sound signals and second carrier currents modulated by television signals, said television carrier at each station being separated from the sound carrier at the same station by a number of signaling channels of other of such stations; a receiving system including circuit means for picking up said television modulated carrier currents and circuit means for picking up said sound modulated carrier currents, each of said circuit means including a condenser having the characteristic of varying the frequency of their respective tuned circuits the same amount per predetermined angular rotation at substantially all the positions of the condenser; and a single means for operating said condensers simultaneously through the same angles.

16. The method of operating a television and sound broadcasting system which comprises transmitting a predetermined television carrier and transmitting a predetermined sound carrier of a different frequency than the television carrier and spaced therefrom a plurality of signaling bands; maintaining the predetermined fixed frequency relation between the carrier of the television signals and the carrier of the corresponding sound signals for each broadcasting station; operating two receivers to maintain a predetermined fixed frequency relation between them corresponding to the frequency relation of the television and sound carriers; operating the receivers to simultaneously tune in to a predetermined television and sound carrier station; and switching the receiver to a different transmitter of television and sound carrier while maintaining the frequency relation between the receivers.

HAROLD M. LEWIS. 

